Carbohydrates

Question 1

Chiral carbohydrates

Answer 1

Optical isomerism occurs when there us asymmetric carbon atom. That is, when a carbon atom has four different groups attached to its four bonds.

Carbohydrates are all based upon the molecular formula (CH2O)n

Each asymmetric carbon atom gives rise to two “mirror images”. The images cannot be superimposed.

Question 2

Properties of sugars

Answer 2

Monosaccharides are reducing sugars. The property of an aldehyde is that it can condense with one molecule of alcohol to form a hemi-acetal. Hemi-acetals can take up a second alcohol to form a full acetal.

A chain compromising up to 8 molecules of a monosaccharide is called an oligosaccharide.

Question 3

Lactose Intolerance

Answer 3

Protein = lactase the enzyme

Carbohydrate = lactose

Most mammals have low levels of the enzyme. So lactose proceeds to colon and bacterial fermentation often occurs in infants.

The symptoms of lactose intolerance can be similar to IBS

Question 4

Uronic acids

Answer 4

Two important uronic acids:
- alpha-D-glucuronic acid
- alpha -D- galacturonic acid

Metabolism and excretion via GLUCURONIDATION :

• the metabolism and excretion of foreign compounds are often referred to as xenobiotics

Question 5

The Beta Link

Answer 5

• the beta link is more stable than the alpha link, more difficult to hydrolyse and when polymerised, forms stable structural polysaccharides.
• the molecular structure of Beta linkages are much more suited to forming fibres